The mountainous forests in arid regions, being sensitive to climate change, are one of the key research topics related to the mechanism of interaction between climate and the terrestrial ecosystem. ...In this study, the spatial distribution of a mid-mountain forest and its environmental factors were investigated by using a combination of remote sensing technology, field survey, climate indices and soil nutrient analysis in the Sangong River watershed of the northern Tianshan Mountains. The forest （Picea schrenkiana） was distributed between 1,510 and 2,720 m asl. Tree height and diameter at breast height （DBH） exhibited a bi-modal pattern with increasing elevation, and rested at 2,450 and 2,250 m asl, respectively. The two maxima of DBH appeared at 2,000 and 2,550 m asl, and the taller trees were observed at 2,100 and 2,600 m asl. For the annual mean temperature, the difference was approximately 5.8℃ between the lowest and the highest limits of the forest, and the average decreasing rates per hundred meters were 0.4g℃ and 0.55℃ with increasing altitude between 1,500 and 2,000 m asl and above 2,000 m asl, respec- tively. The annual precipitation in the forest zone first increased and then decreased with the increase of altitude, and the maximum value was at 2,000 m asl. For per hundred meters, the annual precipitation increased with the rate of 31 mm between 1,500 and 2,000 m asl and decreased by 7.8 mm above 2,000 m asl. The SOM, TN and TP were high between 2,000 and 2,700 m asl and low at the lower and upper forest limits. The minimum CaCO3 con- centration, pH value and EC coincided with the maximum precipitation belt at 2,000 m asl. The SOM, TN and TP were high in the topsoil （0-10 cm） and differed significantly from the values observed in the deep soil layers （〉10 cm）. The soil nutrients exhibited spatial heterogeneity and higher aggregation in the topsoil. In conclusion, soil and climate are closely related to each other, working synergistically to determine the development and spatial distribution of the mid-mountain forest in the study area. The order of the importance of environmental factors to forest development in this study is as follows： soil nutrients〉precipitation〉elevation〉temperature.
In view of the optimal weighting fusion for mean of multi-sensor observation data which needs to obtain accurately observation variance of each sensor and the distribution of weights which has a ...significant effect on the results of fusion, a method of weighted fusion is proposed which estimates the variance in real time and allocates weights dynamically. In order to improve the accuracy of optimal dynamic weighted fusion, a new method of sequential optimal dynamic weighted fusion is proposed. Comparative analysis shows that the accuracy of sequential optimal dynamic weighted fusion is one times higher than that of the optimal dynamic weighted fusion. As an example, we studied the monitoring data of landslide with the method of sequential optimal dynamic weighted fusion, results shows that this method is not only feasible in theory but also more effective than the method of optimal dynamic weighted fusion in practical applications.
Understanding the effect of human activities on the soil environment is fundamental to understanding global change and sustainable development. In the process of transformation of tropical rain ...forests and semiarid grasslands to farmlands, land degradation usually occurs. But the transformation of arid desert landscape to oasis is found to have quite different consequences. Taking an alluvial plain oasis in the north piedmont of the Tianshan Mountains as a case study, we investigate oasis soil properties related to different land-use systems during the transformation of arid desert to oases. Selected land-use systems con- sisted of an annual crop field less than 3 years old, annual crop field 3-6 years old, annual crop field more than 6 years old, perennial crop field less than 4 years old, perennial crop field of 4-6 years old, perennial crop field more than 6 years old, abandoned farmland more than 3 years old, woodland field more than 6 years old, ecological forestation field, natural shrubbery field, desert grass land, and saline or alkaline field. Different land-use systems affect significantly the distribution of sand, silt and clay. Sand content in oasis soil tends to decrease with cultivation years but silt and clay contents tend to be increased in the oasis soils. Soil fertility is higher in the land-use systems under strong human disturbance than under weak human disturbance. Oasis soil nutrients also tend to increase with cultivation years. Soils have a significantly lower salinity in the land-use systems under strong human disturbance than under weak human disturbance. Soil organic matter and nutrients of the annual and perennial crop systems in the oasis tend to increase with cultivation time with the oasis soil acting as a carbon sink. These results show that soils are not degraded and the soil quality is gradually improved under rational land use and scientific management patterns, including uniform exploitation of land resources, effective irrigation systems, sound drainage systems, balanced fertilizer application, crushed straw return to soil and transformation of annual crop fields to perennial ones.
Glutathione (GSH), cysteine (Cys), and homocysteine (Hcy) are small biomolecular thiols that are present in all cells and extracellular fluids of healthy mammals. It is well-known that each plays a ...separate, critically important role in human physiology and that abnormal levels of each are predictive of a variety of different disease states. Although a number of fluorescence-based methods have been developed that can detect biomolecules that contain sulfhydryl moieties, few are able to differentiate between GSH and Cys/Hcy. In this report, we demonstrate a broadly applicable approach for the design of fluorescent probes that can achieve this goal. The strategy we employ is to conjugate a fluorescence-quenching 7-nitro-2,1,3-benzoxadiazole (NBD) moiety to a selected fluorophore (Dye) through a sulfhydryl-labile ether linkage to afford nonfluorescent NBD-O-Dye. In the presence of GSH or Cys/Hcy, the ether bond is cleaved with the concomitant generation of both a nonfluorescent NBD-S-R derivative and a fluorescent dye having a characteristic intense emission band (B1). In the special case of Cys/Hcy, the NBD-S-Cys/Hcy cleavage product can undergo a further, rapid, intramolecular Smiles rearrangement to form a new, highly fluorescent NBD-N-Cys/Hcy compound (band B2); because of geometrical constraints, the GSH derived NBD-S-GSH derivative cannot undergo a Smiles rearrangement. Thus, the presence of a single B1 or double B1 + B2 signature can be used to detect and differentiate GSH from Cys/Hcy, respectively. We demonstrate the broad applicability of our approach by including in our studies members of the Flavone, Bodipy, and Coumarin dye families. Particularly, single excitation wavelength could be applied for the probe NBD-OF in the detection of GSH over Cys/Hcy in both aqueous solution and living cells.
The performance of perovskite photovoltaics is fundamentally impeded by the presence of undesirable defects that contribute to non-radiative losses within the devices. Although mitigating these ...losses has been extensively reported by numerous passivation strategies, a detailed understanding of loss origins within the devices remains elusive. Here, we demonstrate that the defect capturing probability estimated by the capture cross-section is decreased by varying the dielectric response, producing the dielectric screening effect in the perovskite. The resulting perovskites also show reduced surface recombination and a weaker electron-phonon coupling. All of these boost the power conversion efficiency to 22.3% for an inverted perovskite photovoltaic device with a high open-circuit voltage of 1.25 V and a low voltage deficit of 0.37 V (a bandgap ~1.62 eV). Our results provide not only an in-depth understanding of the carrier capture processes in perovskites, but also a promising pathway for realizing highly efficient devices via dielectric regulation.
The highest power conversion efficiencies (PCEs) reported for perovskite solar cells (PSCs) with inverted planar structures are still inferior to those of PSCs with regular structures, mainly because ...of lower open-circuit voltages (
). Here we report a strategy to reduce nonradiative recombination for the inverted devices, based on a simple solution-processed secondary growth technique. This approach produces a wider bandgap top layer and a more n-type perovskite film, which mitigates nonradiative recombination, leading to an increase in
by up to 100 millivolts. We achieved a high
of 1.21 volts without sacrificing photocurrent, corresponding to a voltage deficit of 0.41 volts at a bandgap of 1.62 electron volts. This improvement led to a stabilized power output approaching 21% at the maximum power point.
Lead halide perovskite films have witnessed rapid progress in optoelectronic devices, whereas polycrystalline heterogeneities and serious native defects in films are still responsible for undesired ...recombination pathways, causing insufficient utilization of photon‐generated charge carriers. Here, radiation‐enhanced polycrystalline perovskite films with ultralong carrier lifetimes exceeding 6 μs and single‐crystal‐like electron–hole diffusion lengths of more than 5 μm are achieved. Prolongation of charge‐carrier activities is attributed to the electronic structure regulation and the defect elimination at crystal boundaries in the perovskite with the introduction of phenylmethylammonium iodide. The introduced electron‐rich anchor molecules around the host crystals prefer to fill the halide/organic vacancies at the boundaries, rather than form low‐dimensional phases or be inserted into the original lattice. The weakening of the electron‐phonon coupling and the excitonic features of the photogenerated carriers in the optimized films, which together contribute to the enhancement of carrier separation and transportation, are further confirmed. Finally the resultant perovskite films in fully operating solar cells with champion efficiency of 23.32% are validated and a minimum voltage deficit of 0.39 V is realized.
Ultralong charge‐carrier lifetimes >6 μs are achieved in polycrystalline halide perovskites by decorating the grain boundaries with a trace amount of electron‐rich anchors, which benefits from weak excitonic effects and the weakening of electron–phonon couplings in passivated films, fulfilling reduced voltage deficits and enhanced efficiencies in perovskite photovoltaics. This finding provides a new insight into realizing superior carrier properties of polycrystalline perovskite films and high‐performance perovskite optoelectronics.
Understanding the fundamental properties of buried interfaces in perovskite photovoltaics is of paramount importance to the enhancement of device efficiency and stability. Nevertheless, accessing ...buried interfaces poses a sizeable challenge because of their non‐exposed feature. Herein, the mystery of the buried interface in full device stacks is deciphered by combining advanced in situ spectroscopy techniques with a facile lift‐off strategy. By establishing the microstructure–property relations, the basic losses at the contact interfaces are systematically presented, and it is found that the buried interface losses induced by both the sub‐microscale extended imperfections and lead‐halide inhomogeneities are major roadblocks toward improvement of device performance. The losses can be considerably mitigated by the use of a passivation‐molecule‐assisted microstructural reconstruction, which unlocks the full potential for improving device performance. The findings open a new avenue to understanding performance losses and thus the design of new passivation strategies to remove imperfections at the top surfaces and buried interfaces of perovskite photovoltaics, resulting in substantial enhancement in device performance.
The mystery of the buried interface in perovskite photovoltaics is deciphered by combining advanced spectroscopy techniques with a lift‐off strategy. The findings open a new avenue to understanding performance losses and thus the design of unique passivation strategies to remove imperfections at the top surfaces and buried interfaces of perovskite photovoltaics, resulting in substantial enhancement in device performance.
To deepen the application and development of 3D Printing Construction Technology, the rheological characteristics, compressive strength and bending performance of 3D printed polyvinyl alcohol fiber ...(PVA fiber) reinforced cement-based material were explored. The direction of the intralayer interfaces and the fiber’s distribution direction caused the anisotropy of 3D printed PVA fiber reinforced cement-based material. The printed specimens presented different failure patterns in different compressive directions, and there was certain anisotropy in the X, Y and Z directions. For the bending performance, the load-midpoint deflection curves of casted specimens and the Zx direction of printed specimens showed the strain hardening behavior, while the Zy direction of printed specimens did not. Compared with the Zy specimen, the bending strength of the Zx specimen was about 3 ∼ 4 times higher, and the peak deflection was about an order of magnitude higher. The anisotropy of the printed specimen can be used to improve the bending performance in a specific loading direction to a certain extent.
•The rheological characteristics were used to characterize the Printability.•The printed specimens showed different compressive failure modes.•The direction of intralayer interfaces caused the anisotropy in bending performance.•The fiber’s distribution direction also led to the bending anisotropy.•The microstructure of the printed specimen was denser than the casted specimen.
Plants produce a variety of metabolites that have a critical role in growth and development. Here we present a comprehensive study of maize metabolism, combining genetic, metabolite and expression ...profiling methodologies to dissect the genetic basis of metabolic diversity in maize kernels. We quantify 983 metabolite features in 702 maize genotypes planted at multiple locations. We identify 1,459 significant locus-trait associations (P≤1.8 × 10(-6)) across three environments through metabolite-based genome-wide association mapping. Most (58.5%) of the identified loci are supported by expression QTLs, and some (14.7%) are validated through linkage mapping. Re-sequencing and candidate gene association analysis identifies potential causal variants for five candidate genes involved in metabolic traits. Two of these genes were further validated by mutant and transgenic analysis. Metabolite features associated with kernel weight could be used as biomarkers to facilitate genetic improvement of maize.
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